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Research on Cloud VR Service Experience
Published in Huaping Xiong, Dawei Li, Kun Huang, Mu Xu, Yin Huang, Lingling Xu, Jianfei Lai, Shengjun Qian, Cloud VR, 2020
Huaping Xiong, Dawei Li, Kun Huang, Mu Xu, Yin Huang, Lingling Xu, Jianfei Lai, Shengjun Qian
Smoothness of video and rendering services (for example, gaming) is determined by frame rate. For video services, frame rate is determined by content source. Research shows that 24 FPS is the threshold for smooth videos, and a lower frame rate will affect users. Almost all VR videos can deliver 24 FPS. Unlike animated video images, game images are completely dependent on graphics card (graphics processing unit, GPU) rendering. This means that there are no animated objects in the images. Therefore, to deliver the same level of smoothness as videos, games require a higher rendering frame rate. Moreover, smoothness is related to the terminal screen’s refresh rate. Refresh rate refers to the number of times a terminal can draw a new image on its screen from the GUP in one second. Figure 6.3 shows images at different frame rates.
Input/Output Bank Programming and Interfacing
Published in A. Arockia Bazil Raj, FPGA-Based Embedded System Developer's Guide, 2018
All dot-matrix displays are driven by display data sets via a PNP transistor, typically SK100, array. Each display is connected to separate SIPO shift register via a separate current sinker, for example, ULN2803, to allow larger current to be sunk. Separate modules are built in the FPGA to provide the display data to the transistor array and control bits and clock/clear signals to the SIPO shift register, as shown in Figure 5.4. If a SIPO shift register provides the data sequence “10000000”, that is, 80H, to an HCDTA, the first column in the corresponding dot-matrix display will be connected to ground via ULN2803, and the remaining other columns will be left unconnected. Therefore, LEDs in that column will glow according to the display data. In the same way, the next columns will be driven one by one with the corresponding display data set and control sequence. By building the suitable architecture in the FPGA, we can make the text display scroll. As per the persistence of vision phenomenon, which scientifically determined that a rate of less than 16 frames per second causes the mind to see a flashing character/images, the refresh rate should be equal to at least 24 frames per second. One frame takes 1/24 second to scan all the columns in the matrix. The character scrolling speed can be varied using a potentiometer (POT) and A/D convertor. Details about A/D interfacing and more of its applications can be found in Chapter 7.
Quality Criteria for Simulator Images: A Literature Review
Published in Florian Jentsch, Michael Curtis, Eduardo Salas, Simulation in Aviation Training, 2017
Pieter Padmos, Maarten V. Milders
Update frequency is the frequency with which a totally new image content is generated (AGARD, 1981). Refresh rate (also called frame rate) is the frequency with which a whole frame of the display is written (Rolfe and Staples, 1986). Occasionally these quantities are confused in the literature. A low update frequency causes shaky moving images or distortion of contours; a low refresh rate causes luminance flicker. In modern CGI systems with a double frame buffer, the refresh rate can be higher than the update frequency. Generally, the refresh rate is kept at a fixed frequency, whereas the update frequency may be the refresh rate divided by a whole number, depending on the scene complexity (Rolfe and Staples, 1986).
A novel monitor for practical brain-computer interface applications based on visual evoked potential
Published in Brain-Computer Interfaces, 2021
Hamidreza Maymandi, Jorge Luis Perez Benitez, F. Gallegos-Funes, J. A. Perez Benitez
Most of the VEP-based studies employ a computer monitor as the visual stimulator. Since conventional monitors are not designed for BCI applications, they are limited in their ability to generate RVSs. Furthermore, some studies have shown that newer-generation monitors increase the cost of signal processing. This is due to the conflicts with complex technological processes that are used in these new monitors to realize improved video output. In 2009, Husain et al. [11] made a comparison between cathode ray tube (CRT) and liquid crystal display (LCD) and found out that CRTs have better performance in stimulating pattern reversal visual evoked potentials. Adam Wilson et al. [12] showed that despite LCDs being more convenient in terms of size, weight, and movability, the increased time latency and variability of output timing provoke computation difficulties. The sort of studies developed by Nagel et al. [13] showed all VEP-based BCIs using a standard monitor are affected by the raster latency regardless of whether they are based on cVEP, SSVEP, or P300. Raster latency is the delay to update each line of the image sequentially depending on the refresh rate [14]. Furthermore, the refresh rate is an additional factor of image processing performed in the monitor itself [12]. The refresh rate is the number of times per second that a display updates the screen. Effectively, the frequency of flickering in a BCI is restricted to less than half of the refresh rate of a monitor [4,15,16]. Because the black/white reversal needs to occur every 2.73 frames, realizing frequencies that are not integer fractions of the refresh rate is impossible [15]. So, the refresh rate not only limits the bandwidth of VEP frequency [17] but also the number of the possible target [16,18]. Each one of these deficiencies causes user discomfort and decreases the performance of BCI systems.
Comparison of visual fatigue caused by head-mounted display for virtual reality and two-dimensional display using objective and subjective evaluation
Published in Ergonomics, 2019
Masakazu Hirota, Hiroyuki Kanda, Takao Endo, Tomomitsu Miyoshi, Suguru Miyagawa, Yoko Hirohara, Tatsuo Yamaguchi, Makoto Saika, Takeshi Morimoto, Takashi Fujikado
A conventional 2D display (GL2460, BenQ Corp., Taiwan) was used as a control. The GL2460 is equipped with a 24-inch liquid crystal display with a resolution of 1920 × 1080 pixels (angle of view at 2.0 m, 15.7°). The refresh rate is 60 Hz.